In recent years, an increase in size of a wafer is demanded, and a wire saw apparatus is mainly used to slice a work with this increase in size.
The wire saw apparatus is an apparatus that causes a wire (a high-tensile steel wire) to travel at a high speed and presses a work against the wire to be sliced while applying a slurry to the wire, thereby slicing the work into many wafers at the same time (see Japanese Unexamined Patent Publication (Kokai) No. 262826-1997).
Here, FIG. 7 shows an outline of an example of a conventionally general wire saw apparatus.
As shown in FIG. 7, a wire saw 101 mainly includes a wire 102 for slicing an work, grooved rollers 103 around which the wire 102 is wound, a mechanism 104 for giving the wire 102 a tensile force, a mechanism 105 for feeding the work to be sliced downward, and a mechanism 106 for supplying a slurry at the time of slicing.
The wire 102 is unreeled from one wire reel 107 and reaches the grooved rollers 103 through the tensile-force-giving mechanism 104 formed of a powder clutch (a constant torque motor 109), a dancer roller (a dead weight) (not shown) and so on through a traverser 108. The wire 102 is wound around this grooved rollers 103 for approximately 300 to 400 turns, and then taken up by a wire reel 107′ through the other tensile-force-giving mechanism 104′.
Moreover, each of the grooved rollers 103 is a roller that has a steel cylinder of which a polyurethane resin is pressed in peripheral part and has grooves formed at a fixed pitch on a surface thereof, and the wound wire 102 can be driven in a reciprocating direction in a predetermined cycle by a driving motor 110.
It is to be noted that such an work-feeding mechanism 105 as shown in FIG. 8 feeds the work toward the wire 102 wound around the grooved rollers 103 by holding and pushing down the work at the time of slicing the work. This work-feeding mechanism 105 includes an work-holding portion 111 that is used to hold and push down the work and an LM guide 112. Driving the work-holding portion 111 along the LM guide 112 under control of a computer enables feeding the work at a previously programmed feed speed.
It is to be noted that the work is adhered to a pad plate 114. The pad plate 114 is held by a work plate 113. The work is held by the work-holding portion 111 through the pad plate 114 and the work plate 113.
Moreover, as shown in FIG. 7 nozzles 115 are provided near the grooved rollers 103 and the wound wire 102, and a slurry can be supplied to the wire 102 from a slurry tank 116 at the time of slicing. Additionally, a slurry chiller 117 is connected with the slurry tank 116 so that a temperature of the slurry to be supplied can be adjusted.
With the wire saw apparatus 101, an appropriate tensile force is applied to the wire 102 by the tensile-force-giving mechanism 104, and the work is sliced while the wire 102 is caused to travel in a reciprocating direction by the driving motor 110.
However, the present inventor sliced the work into wafers using the general wire saw apparatus as described above and examined a shape of the sliced wafer. As a result, a large Warp was generated. The Warp is one of an important quality for slicing of a semiconductor wafer. Thus, the more quality demand of a product increases, the more demand of reduction of the Warp increases.